Smart switching using multispectral imaging

ABSTRACT

A multispectral sensor is provided with an illumination source and a digital imaging system. The illumination source is disposed to provide light at multiple wavelengths to an object. The digital imaging system is disposed to receive light scattered from the object and has a digital array of light detectors and a color filter array. The color filter array has a multiple distributed filter elements, each of which is adapted to transmit light of one of a limited number of specified narrowband wavelength ranges. The color filter array is disposed to filter the light scattered from the object prior to encountering the digital array of light detectors.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent application Ser. No. 10/818,698, entitled “MULTISPECTRAL BIOMETRIC SENSOR,” filed Apr. 5, 2004 by Robert K. Rowe et al. (“the '698 application”), the entire disclosure of which is incorporated herein by reference for all purposes. The '698 application is a nonprovisional of, and claims the benefit of the filing date of each of the following provisional applications, the entire disclosure of each of which is incorporated herein by reference for all purposes: U.S. Prov. Pat. Appl. No. 60/460,247, entitled “NONINVASIVE ALCOHOL MONITOR,” filed Apr. 4, 2003; U.S. Prov. Pat. Appl. No. 60/483,281, entitled “HYPERSPECTRAL FINGERPRINT READER,” filed Jun. 27, 2003 by Robert K. Rowe et al.; U.S. Prov. Pat. Appl. No. 60/504,594, entitled “HYPERSPECTRAL FINGERPRINTING,” filed Sep. 18, 2003; and U.S. Prov. Pat. Appl. No. 60/552,662, entitled “OPTICAL SKIN SENSOR FOR BIOMETRICS,” filed Mar. 10, 2004 by Robert K. Rowe.

This application is also related to U.S. patent application Ser. No. 09/874,740, entitled “APPARATUS AND METHOD OF BIOMETRIC DETERMINATION USING SPECIALIZED OPTICAL SPECTROSCOPY SYSTEM,” filed Jun. 5, 2001, and to U.S. Prov. Pat. Appl. No. 60/576,364, entitled “MUSTISPECTRAL FINGER RECOGNITION,” filed Jun. 1, 2004 by Robert K. Rowe and Stephen P. Corcoran, the entire disclosures of both of which are incorporated herein by reference for all purposes.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

The Government of the United States may have rights in this invention.

BACKGROUND OF THE INVENTION

This application relates generally to biometrics. More specifically, this application relates to methods and systems for performing biometric measurements with a multispectral imaging sensor.

“Biometrics” refers generally to the statistical analysis of characteristics of living bodies. One category of biometrics includes “biometric identification,” which commonly operates under one of two modes to provide automatic identification of people or to verify purported identities of people. Biometric sensing technologies measure the physical features or behavioral characteristics of a person and compare those features to similar prerecorded measurements to determine whether there is a match. Physical features that are commonly used for biometric identification include faces, irises, hand geometry, vein structure, and fingerprint patterns, which is the most prevalent of all biometric-identification features. Current methods for analyzing collected fingerprints include optical, capacitive, radio-frequency, thermal, ultrasonic, and several other less common techniques.

Most of the fingerprint-collection methods rely on measuring characteristics of the skin at or very near the surface of a finger. In particular, optical fingerprint readers typically rely on the presence or absence of a difference in the index of refraction between the sensor platen and the finger placed on it. When an air-filled valley of the fingerprint is above a particular location of the platen, total internal reflectance (“TIR”) occurs in the platen because of the air-platen index difference. Alternatively, if skin of the proper index of refraction is in optical contact with the platen, then the TIR at this location is “frustrated,” allowing light to traverse the platen-skin interface. A map of the differences in TIR across the region where the finger is touching the platen forms the basis for a conventional optical fingerprint reading. There are a number of optical arrangements used to detect this variation of the optical interface in both bright-field and dark-field optical arrangements. Commonly, a single, quasimonochromatic beam of light is used to perform this TIR-based measurement.

There also exists non-TIR optical fingerprint sensors. In most cases, these sensors rely on some arrangement of quasimonochromatic light to illuminate the front, sides, or back of a fingertip, causing the light to diffuse through the skin. The fingerprint image is formed due to the differences in light transmission across the skin-platen boundary for the ridge and valleys. The difference in optical transmission are due to changes in the Fresnel reflection characteristics due to the presence or absence of any intermediate air gap in the valleys, as known to one of familiarity in the art.

Optical fingerprint readers are particularly susceptible to image quality problems due to non-ideal conditions. If the skin is overly dry, the index match with the platen will be compromised, resulting in poor image contrast. Similarly, if the finger is very wet, the valleys may fill with water, causing an optical coupling to occur all across the fingerprint region and greatly reducing image contrast. Similar effects may occur if the pressure of the finger on the platen is too little or too great, the skin or sensor is dirty, the skin is aged and/or worn, or overly fine features are present such as may be the case for certain ethnic groups and in very young children. These effects decrease image quality and thereby decrease the overall performance of the fingerprint sensor. In some cases, commercial optical fingerprint readers incorporate a thin membrane of soft material such as silicone to help mitigate some of these effects and restore performance. As a soft material, the membrane is subject to damage, wear, and contamination, limiting the use of the sensor without maintenance.

Biometric sensors, particularly fingerprint biometric sensors, are generally prone to being defeated by various forms of spoof samples. In the case of fingerprint readers, a variety of methods are known in the art for presenting readers with a fingerprint pattern of an authorized user that is embedded in some kind of inanimate material such as paper, gelatin, epoxy, latex, and the like. Thus, even if a fingerprint reader can be considered to reliably determine the presence or absence of a matching fingerprint pattern, it is also critical to the overall system security to ensure that the matching pattern is being acquired from a genuine, living finger, which may be difficult to ascertain with many common sensors.

A common approach to making biometric sensors more robust, more secure, and less error-prone is to combine sources of biometric signals using an approach sometimes referred to in the art as using “dual,” “combinatoric,” “layered,” “fused,” or “multifactor biometric sensing. To provide enhanced security in this way, biometric technologies are combined in such a way that different technologies measure the same portion of the body at the same time and are resistant to being defeated by using different samples or techniques to defeat the different sensors that are combined. When technologies are combined in a way that they view the same part of the body they are referred to as being “tightly coupled.”

There is accordingly a general need in the art for improved methods and systems for biometric sensing.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the invention provide a multispectral sensor that comprises an illumination source and a digital imaging system. The illumination source is disposed to provide light at a plurality of wavelengths to an object. The digital imaging system is disposed to receive light scattered from the object and comprises a digital array of light detectors and a color filter array. The color filter array has a plurality of distributed filter elements, each of which is adapted to transmit light of one of a limited number of specified narrowband wavelength ranges. The color filter array is disposed to filter the light scattered from the object prior to encountering the digital array of light detectors.

The multispectral sensor may function as a biometric sensor when the object comprises a skin site of an individual, and may be configured to detect blanching or blood pooling at the skin site as part of a spoof detection. In some instances, the filter elements are distributed according to a Bayer pattern. In some embodiments, a first polarizer may be disposed to polarize the light provided by the illumination source, with the digital imaging system further comprising a second polarizer disposed to polarize the light scattered from the object. The first and second polarizers may advantageously be provided in a crossed configuration.

The multispectral sensor may be incorporated within a portable electronic device and have such functionality as an ability to read a bar code, an ability to scan printed matter, an ability to securely receive data related to functionality changes of the portable electronic device, and the like. In other instances, the multispectral sensor may be configured for use as a smart switch, configured for use as a pointing device, configured for use a text entry device, configured for measuring an ambient light condition, and the like. In some embodiments, the multispectral sensor is integrated with a separate biometric sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the drawings wherein like reference labels are used throughout the several drawings to refer to similar components. In some instances, reference labels include a numerical portion followed by a latin-letter suffix; reference to only the numerical portion of reference labels is intended to refer collectively to all reference labels that have that numerical portion but different latin-letter suffices.

FIG. 1 provides a front view of a multispectral biometric sensor in one embodiment of the invention; and

FIG. 2 provides a front view of a multispectral biometric sensor shown in another embodiment.

DETAILED DESCRIPTION OF THE INVENTION 1. Overview

Embodiments of the invention provide methods and systems that allow for the collection and processing of biometric measurements. These biometric measurements may provide strong assurance of a person's identity, as well as of the authenticity of the biometric sample being taken, and may be incorporated within a number of different types of devices, such as cellular telephones, personal digital assistants, laptop computers, and other portable electronic devices. In some embodiments, a sensor provides light that penetrates the surface of an individual's skin, and scatters within the skin and/or underlying tissue. Skin sites applicable to multispectral imaging and biometric determination include all surfaces and all joints of the fingers and thumbs, the fingernails and nail beds, the palms, the backs of the hands, the wrists and forearms, the face, the eyes, the ears, and all other external surfaces of the body. While the discussion below sometimes makes reference to “fingers,” it should be understood that this refers merely to exemplary embodiments and that other embodiments may use skin sites at other body parts.

A portion of the light scattered by the skin and/or underlying tissue exits the skin and is used to form a multispectral image of the structure of the tissue at and below the surface of the skin. As used herein, the term “multispectral” is intended to be construed broadly as referring to methods and systems that use multiple wavelengths, and thus includes imaging systems that are “hyperspectral” or “ultraspectral” as those terms are understood by those of skill in the art. Because of the wavelength-dependent properties of the skin, the image formed from each wavelength of light is usually different from images formed at other wavelengths. Accordingly, embodiments of the invention collect images from each of the wavelengths of light in such a way that characteristic spectral and spatial information may be extracted by an algorithm applied to the resulting multispectral image data.

Embodiments of the invention provide for multispectral imaging of tissue using a digital imaging system. An illustration of a simplified arrangement is shown in FIG. 1, which shows one embodiment for a multispectral biometric sensor 101. The multispectral sensor 101 comprises one or more sources of light 103 and a digital imaging system 123. The number of illumination sources may conveniently be selected to achieve certain levels of illumination, to meet packaging requirements, and to meet other structural constraints of the multispectral biometric sensor 101. Illumination passes from the source 103 through illumination optics that shape the illumination to a desired form, such as in the form of flood light, light lines, light points, and the like. The illumination optics 105 are shown for convenience as consisting of a lens but may more generally include any combination of one or more lenses, one or more mirrors, and/or other optical elements. The illumination optics 105 may also comprise a scanner mechanism (not shown) to scan the illumination light in a specified one-dimensional or two-dimensional pattern. The light source 103 may comprise a point source, a line source, an area source, or may comprise a series of such sources in different embodiments.

After the light passes through the illumination optics 105, it passes through a platen 117 and illuminates the finger 119 or other skin site so that reflected light is directed to a digital imaging system 123. The digital imaging system 123 generally comprises a digital array 115 and detection optics 113 adapted to focus the light reflected from the object onto the array. For example, the detection optics 113 may comprise a lens, a mirror, a pinhole, combination of such optical elements, or other optical elements known to those of skill in the art. The digital imaging system 123 also comprises a color filter array 121, which may in some instances be incorporated as part of the digital array 115. The color filter array 121 may comprise a red-green-blue filter array in the well-known Bayer pattern or in other patterns. In some instances, the filter elements may function to transmit wavelengths that differ from the standard red-green-blue wavelengths, may include additional wavelengths, and/or may be arranged in a pattern that differs from the Bayer pattern. In instances where such a color filter array 121 is included, the illumination source(s) 103 may be a white-light or broadband source. Alternatively, the illumination source(s) 103 may comprise a plurality of narrowband sources, such as LEDs, with central wavelengths that are within the pass bands of filter elements comprised by the color filter array 121.

The sensor layout and components may advantageously be selected to minimize the direct reflection of the illumination into the digital imaging system 123. In one embodiment, such direct reflections are reduced by relatively orienting the illumination and detection optics such that the amount of directly reflected light detected is minimized. For instance, optical axes of the illumination optics 105 and the detection optics 113 may be placed at angles such that a mirror placed on the platen 117 does not direct an appreciable amount of illumination light into the detection subsystem 123. In addition, the optical axes of the illumination and detection optics may be placed at angles relative to the platen 117 such that the angular acceptance of both subsystems is less than the critical angle of the system; such a configuration avoids appreciable effects due to total internal reflectance between the platen 117 and the skin site 119.

The specific characteristics of the optical components comprised by the multispectral sensor 101 may be implemented to configure the multispectral sensor 101 for different form factors. For example, in an embodiment where the multispectral sensor is implemented in the top of a gear shift as part of a system to verify the identify of a driver of a vehicle, the light sources 103 and digital array 115 might not fit within the gear-shift handle as constructed. In such an embodiment, an optical relay system may be implemented. For example, relay optics that comprise individual lenses similar to those in a bore scope may be used, or alternatively optical fibers such as used in orthoscopes may be used. Still other techniques for implementing an optical relay system will be evident to those of skill in the art. In this way, components of the sensor may be located remotely from the sampling surface.

The multispectral sensor may take multiple images and combine them for processing. For example, one image may be made with one or more illumination wavelengths present and be followed immediately by an image taken with no illumination turned on. The difference between these two images allows the effect of illumination to be separated from background illumination. The difference image may then be used for further processing according to other aspects of the invention.

In some embodiments, the multispectral sensor uses optical polarizers. One example of such an embodiment is provided in FIG. 2. The basic structure of the sensor 101′ is similar to that of FIG. 1, but polarizers 107 have been added to the illumination system(s) 121 and a polarizer 111 has been added to the digital imaging system. The polarizers 107 and 111 may be linear or circular, or a combination of the two. In the case of linear polarizers, one useful arrangement is that in which the illumination light is polarized along a particular axis while the detected light requires an orthogonal polarization. Such an arrangement has utility in ensuring that detected light has undergone multiple scatter events in a medium such as skin. Further utility is derived from the observation that such an arrangement greatly reduces the visibility of latent prints left on the platen 117 by previous users, thus providing improved image quality and reducing the likelihood of spoofing by “reactivating” the latent prints. The utility of the arrangement also extends to conventional optical fingerprint readers as well as multispectral imagers. In particular, dark-field optical fingerprint systems are well-suited for the addition of linear polarizers in such an arrangement. Further discussion of a multispectral finger-recognition sensor that uses such a crossed-polarizer arrangement is described in copending, commonly assigned U.S. Prov. Pat. Appl. No. 60/576,364, entitled “MULTISPECTRAL FINGER RECOGNITION,” filed Jun. 1, 2004 by Robert K. Rowe and Stephen P. Corcoran, the entire disclosure of which is incorporated herein by reference for all purposes.

2. Applications

In a number of specific embodiments, A multispectral imaging sensor may be incorporated in a cellular telephone, a personal digital assistant, a laptop computer, or other portable electronic device. Such a multispectral sensor may be configured to collect multispectral biometric data on a finger. The sensor may require that a person touch the sensor, or may be able to collect the necessary multispectral data in a noncontact fashion with appropriate images being collected while the skin is located at a distance from the sensor.

In some embodiments, the multispectral imaging sensor incorporated in a portable electronic device may contain an optical system to enable adjustable focus. The mechanism for adjusting the may include one or more lenses that may be moved into various positions. The focusing mechanism itself may be a conventional zoom arrangement. Alternatively, the mechanism for focusing may use a liquid lens based on the known phenomenon of electro-wetting.

In a system configuration in which the portable electronic device has been designed to accommodate a “close-up” or macro image of the finger for biometric sensing, the same optical system may be used to read an optical code such as a barcode. Such a barcode reading could, for example, initiate a service in which product information for a product corresponding to the UPC barcode is downloaded to the portable device to provide the consumer with comparative pricing and performance data. Similar barcode scans may be used in other embodiments for promotional games or various gaming activities. The conjunction of a barcode scan taken in close temporal proximity to a biometric scan could provide for an audit trail for legal matters, including financial documents and transactions, forensic chain-of-evidence scenarios, and a variety of logical and/or physical security applications.

An imaging system on a portable electronic device that is configured to collect multispectral biometric data may also be used to scan in text, graphics, or other printed matter. In the case of text, the scanned data may be converted to an interpretable form using known optical-character-recognition (“OCR”) techniques. Such text recognition may then be used to provide input of text-translation services, copying services, and other such services that may be aided by a rapid and convenient character input.

An imaging system on a portable electronic device may also be used as an optical input device to provide a mechanism for securely inputting data into the device for functions such as reprogramming, security overrides, and secure digital communications. The illumination components of the imaging system may be used as optical output devices in the reverse direction from the detector elements. The use of multiple, filtered wavelengths can provide proved for multiple high-bandwidth channels for rapid and/or robust optical communication.

The multispectral sensor may also be used as a smart switch to turn on or enable an associated device, system, or service. In such a capacity, the multispectral sensor may be set to a video-streaming mode to collect several frames per second. Each frame may then be analyzed to detect motion and, if motion is detected, perform image processing steps to confirm that the motion is due to a finger by analyzing the overall shape, the texture, and/or the spectral qualities relative to a living finger.

The multispectral sensor may be used as a pointing device with similar functionality as a touchpad commonly used on a laptop PC. The multispectral sensor can be used in this fashion by monitoring the motion of the finger over the sensing area. Sliding the finger in a linear motion to the left can indicate a leftward motion to the PC (or cell phone, PDA, or other device), with similar effects for motions to the right, up, down, diagonal, or other directions. The cursor of the PC (or cell phone, PDA, or other device) may then be made to move in the indicated direction, or other appropriate action may be taken. In a similar fashion, the surface of the sensor may be tapped in different regions to simulate a click or double-click of a conventional PC mouse. Other motions, such as circles, X's, and the like, may be used to indicate other specific actions. In the case of touching or tapping the sensor, the degree of pressure may be estimated by evaluating the degree of blanching occurring in the finger. In this manner, different actions may be taken in response to a soft pressure being sensed relative to a hard pressure.

The spectral qualities of the finger in motion may be assessed to ensure that the detected motion is from that of a finger rather than some spurious object. In this way, false motions can be avoided.

The sensor surface may also be used as a simple text entry device. In a similar fashion as in the case of a pointing device, the user may make motions with the fingertip that describe single letters or number, which are then accumulated by the portable electronic device.

A particular motion of the finger may be used to increase the security of the sensing system. In such a configuration, the spectral and spatial qualities of the finger are confirmed to match those that are on record while the particular finger motion that is made is assessed to ensure it is similar to the motion on record. In this way, both the finger qualities and the motion need to match in order to determine an overall match.

The multispectral sensor may be used to measure the ambient light condition. In order to do so, an image is taken without any illumination light turned on at a time when a finger is not covering the sensor surface. The amount of ambient light may be determined from the image. Further details about ambient lighting may be derived in the case where the imager uses a color filter array or a similar mechanism to assess spectral characteristics of the light. The measure levels of ambient light may then be used by the associated device to set levels for display brightness, backlighting, etc. Such settings are particularly useful in ensuring the usability of portable electronic devices while conserving battery usage.

3. Combinations of Multispectral Sensing with Other Biometric Sensors

A small and rugged embodiment of a multispectral sensor may be constructed from solid-state components such as silicon digital imaging arrays and light-emitting diodes. Such a sensor may be integrated into a conventional fingerprint sensor to provide a second biometric reading when a fingerprint is taken. The conventional fingerprint sensor may be an optical fingerprint sensor. The multispectral sensor may use one or more illumination wavelengths to sense optical characteristics of the skin, including the presence, degree, and/or distribution of blood in the finger or other body part. The illumination wavelength(s) may include one or more wavelengths shorter than approximately 600 nm, where blood is known to become highly optically absorbing and thus discernible from other tissue components.

The images taken by the multispectral sensor prior to the finger touching the sensor may be used in whole or in part to perform a biometric assessment of the person's identity. In the case of a fingerprint, the individual ridge lines may be identified and tracked through a series of images to quantify the degree and type of distortion that such ridge images undergo when pressure is applied to the sensor by the finger.

The fingerprint pattern observed by the multispectral imager using one or more illumination wavelengths may be combined with the TIR pattern to provide a combinatoric biometric. The multispectral image may contain information on the external friction ridge pattern, the internal friction ridge pattern, the composition and position of other subsurface structures, the spectral qualities of the finger, the size and shape of the finger, and other features that are somewhat distinct from person to person. In this way, one or more multispectral features may be combined with the optical fingerprint data to provided additional biometric information.

In some cases, the multispectral imaging data may be processed to improve the quality of the TIR fingerprint. In particular, there may be a linear or nonlinear numerical relationship established on parts of the image where both the multispectral image data and TIR data are well defined. These parts are then used to establish a mathematical model such as with Principal Component Regression, Partial Least Squares, Neural Networks, or other methods to one familiar in the art. The parts of the TIR image that are missing due to poor contact, etc. can thus be estimated from the model so established. In another embodiment, the entire images may be used, but the numerical model built using robust statistics in which the relationship is relatively unaffected by missing or degraded portions of the TIR image. Alternatively, numerical models may be established through the examination of previously collected TIR/multispectral image sets and then applied to new data.

4. Spoof Detection

The multispectral sensor may be used to make a determination about the authenticity of the sample and thereby detect attempts to spoof the optical fingerprint sensor. The multispectral sensor may be able to make a static spectral reading of the sample either when it touches the sensor surface or at a remote distance to ensure that the spectral qualities match those of a living finger.

The multispectral sensor may also use one or more illumination wavelengths to illuminate the finger as it moves to touch the sensor surface. During this interval of time, blanching of the skin may be observed in the vicinity of the sensor as pressure is applied by the finger. As well, areas of the skin may show a distinct pooling of blood, especially those regions at the perimeter of the area of contact between the finger and sensor. This blanching and/or pooling of the skin provides an identifiable set of changes to the corresponding images. In particular, wavelengths less than approximately 600 nm, which are highly absorbed by the blood, are seen to get brighter in the region of blanching and darker in areas of blood pooling. Wavelengths longer than approximately 600 nm are seen to change much less during blanching and/or pooling. The presence, magnitude, and/or relative amounts of spectral changes that occur while the finger touches the fingerprint sensor can be used as an additional means of discriminating between genuine measurements and attempts to spoof the sensor.

In the case where the multispectral sensor is combined with an optical TIR fingerprint reader, the pattern detected by the multispectral sensor using one or more illumination wavelengths may be compared with the pattern detected by the fingerprint sensor and consistency confirmed. In this way, the internal fingerprint data due to blood and other subsurface structures is used to confirm the image of the external fingerprint that the conventional fingerprint sensor collects. If there is a discrepancy between the two patterns, an attempt to spoof the fingerprint sensor using a thin, transparent film placed on the finger may be indicated. Appropriate action may be taken in response to this discrepancy to ensure that such a spoof attempt is not being perpetrated.

Other factors that can be monitored to discriminate between genuine finger and attempts to spoof the detector using an artificial or altered sample of some kind include monitoring the image taken with 1 or more wavelengths over time. During the specified time interval, changes such as those due to pulse can be measured and used to confirm a genuine finger. As well, changes in the image due to sweating at the ridge pores can be observed and used for spoof detection.

Thus, having described several embodiments, it will be recognized by those of skill in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the invention. Accordingly, the above description should not be taken as limiting the scope of the invention, which is defined in the following claims. 

1.-17. (canceled)
 18. A multispectral smart switch comprising: a switch in electrical communication with an associated device and having a platen; and an imaging system disposed to image an object in proximity to the platen, and to determine, according to the image, whether the object is a finger, the switch disposed to enable a function of the associated device only when the object is determined to be a finger.
 19. The smart switch of claim 18, further comprising: an illumination source disposed to provide light at a plurality of wavelengths to an object in proximity to the platen, wherein the imaging system is disposed to image the object by receiving light scattered from the object.
 20. The smart switch of claim 19, wherein the imaging system is further disposed to determine whether the object is a finger by analyzing or one or more multispectral qualities of the object from the image.
 21. The smart switch of claim 18, wherein the imaging system is further disposed to: collect a sequence of image frames; and analyze the sequence of image frames to detect a motion, wherein the imaging system is disposed to determine whether the object is a finger according to the motion.
 22. The smart switch of claim 21, wherein the imaging system is further disposed to determine whether the object is a finger according to the motion by analyzing the motion relative to that of a living finger.
 23. The smart switch of claim 21, wherein the imaging system is further disposed to determine whether the object is a finger according to the motion by analyzing an overall shape of the object from the sequence of image frames.
 24. The smart switch of claim 21, wherein the imaging system is further disposed to determine whether the object is a finger according to the motion by analyzing a texture of the object from the sequence of image frames.
 25. The smart switch of claim 21, wherein the imaging system is further disposed to determine whether the object is a finger according to the motion by analyzing or one or more spectral qualities of the object from the sequence of image frames.
 26. A method for enabling a function of an associated device using a multispectral smart switch, the method comprising: imaging an object in proximity to a platen of a switch in electrical communication with the associated device determining, according to the imaging, whether the object is a finger; and enabling the function of the associated device only when the object is determined to be a finger.
 27. The method of claim 26, further comprising: illuminating the object with light at a plurality of wavelengths when the object is in proximity to the platen, wherein the imaging comprises receiving light scattered from the object.
 28. The method of claim 27, wherein determining whether the object is a finger comprises analyzing or one or more multispectral qualities of the object derived from the received scattered light.
 29. The method of claim 26, further comprising: collecting a sequence of image frames; and analyzing the sequence of image frames to detect a motion, wherein the determining whether the object is a finger is according to the motion.
 30. The method of claim 29, wherein the determining whether the object is a finger according to the motion comprises analyzing the motion relative to that of a living finger.
 31. The method of claim 29, wherein the determining whether the object is a finger according to the motion comprises analyzing an overall shape of the object from the sequence of image frames.
 32. The method of claim 29, wherein the determining whether the object is a finger according to the motion comprises analyzing a texture of the object from the sequence of image frames.
 33. The method of claim 29, wherein the determining whether the object is a finger according to the motion comprises analyzing or one or more spectral qualities of the object from the sequence of image frames. 